Some finds I'm wondering about.

benjen

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Apr 26, 2004
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My wife and I have made some finds in our tank recently and I though I'd describe the to see if others have any ideas where I should start looking for their identities and care. No pictures because my digital camera wouldn't show anything that small as more than a blur.

Under the sand:
- First I saw one critter picking up sand grains against the glass and presumably cleaning algae/bacteria off. It had what certainly looked like crab claws a few mm long, but I got no glimpse of the body. Assuming some form of sand-dwelling crab.
- The second I was afraid was a spearer mantis at first because it has many pairs of legs and was manipulating some tiny shells with forelimbs that were three-segmented in a pattern vaguely similar to a terrestrial mantid's. However, I remembered that this would be upside down for a mantis shrimp and am now guessing maybe a sand-dwelling isopod dining on algae. I haven't seen the body, but I've seen at least 7-9 pairs of 2-3 mm legs and it doesn't have claws I've spotted so far. I'm guessing at least 1 cm long.

Under an overhang:
- This is the one I'm more concerned about, as the others seem to be scavengers. I saw what looks like 3-4 tiny bright red branches. Each one has a stouter base (2 mm) with smaller branches sticking out. The larger branches also have branches. The texture could point to a sponge, but I did not see the single larger opening that most sponges I'm familiar with have. The largest one looks like a baby coral of some sort to me, possibly a tree coral hanging upsaide down. This ledge is by where the currents of 2 powerheads hit the front of the tank and turn back, so plenty of erratic current, but I'm concerned that I've got a baby coral that may be a pure filter-feeder. I can't see it without crouching and using a flashlight (my wife spotted it), but I figured there might be some ideas of what could just spring up in that spot and match the description. No obvious tentacles spotted yet.

Any thoughts?
 
Here are some guesses to get things rolling:

Thing 1 (wild guess) some kind of nereid or eunicid worm. Their jaws look a lot like claws. Did you see two claws?

Thing 2 (less wild guess) an amphipod. Here's one from Museum Victoria, with claws and a lot of legs:
mov370i.html

There are others on their amphipod pic page here

Stumped on the last one. Bryozoan? Sponge? Macroalgae? Maybe a sketch would help.
 
Thing 1: 2 claws working in apparent tandem spotted once. Did not look like the pictures of nereids or eucinids I just googled. Looked more like tiny, semi-transparent (or sand colored) versions of my emerald crab's claws. If it was a worm, it didn't have any visible segments until you got back to where the first segment would be in a crab's arm (excepting the 'hinge' that allows the claw to work). The movements also seemed crablike.

Thing 2: OK. It is different from my plentiful gammarus species, but I basically only see the bottom/side, so a couple of those could be it, although the legs I've seen appeared to be of more uniform length than I'm used to in amphipods.


ASCII Art attempt:
__________
.....|...|.....
...././.\.\....
...//\\...\\_.
../\..|\../.\.

The largest example of Thing 3 looks a bit like the above, with each line being about a mm or 2. No tentacles visible anywhere when I shine a light, but bright red at the base fading to pale/transparent at the very tips or just too small to see color. Only two main branches so far, but the others only have one 'trunk'. Maybe it's a macroalgae that looks unusually coralish. I'm just surprised that a more complex macro would grow in the highest combo of current + lower light in the tank, pretty much. Good spot for a deeper water one, though.
 
Thing 1: Looked at Reefkeeping Mag earlier and noticed the article on amphipods. Apparently a few species have what are called "chelate" appendaged on the second gnathopod. This appendage could possibly be the claws I saw, as it has the right shape. It's figure 7 to see them.
http://reefkeeping.com/issues/2004-09/rs/index.htm

Thing 2: My wife spotted it above sand for a moment and I also saw it. Definately an amphipod or isopod. Looked a bit like a skinny, sand-colored pill bug in the brief glance I got. Lacked the strong 'C' curvature of most gammarus-like amphipods I've seen.

Thing 3: No new clues.
 
I got one (maybe more) of those Tanaid(s) in my nano. They seem to hang out on some of the macro algae I have at night.

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